Bonded product with long temperature range binders



Patented Sept.' 15, 1936 PATENT OFFICE BONDED PRODUCT WITH LONG TEM- f PERATURE RANGE BINDERS Willis A. Boughton,

Mansfield, Boston,

Cambridge, and William Mass., assignors to New England Mica C0., Waltham, Mass., a corpoeration of Massachusetts Original application October 1, 1934, Serial No. 746,476. Divided and this application June 27, 1935, Serial No. 28,766

14 Claims.

This invention relates to molded and bonded products containing discrete particles" of solids, such for example as asbestos fibres, and mica akes, vbonded together with types of mixed binders, for example binders containing cooperating organic and inorganic constituents, 'the bonded products being useful in the arts, and remaining integrated over a wide range of ternperatures; this application being a division from our co-pending application for Binders of mixed yls, Serial Number 746,476, led October 1st, An obj ect of the invention is to provide products made of discrete particles of matter bonded together with a new type of binder, the products being capable of withstanding wide temperature changes, ranging from ordinary temperatures to those approaching a red heat, without loss of integration, or impairment of other useful properties.

A further object is to provide laminated mica products, for example built-up mica sheets, bound with a new type of mixed binder, the constituents of which are cooperating organic and inorganic substances, possessing all the advantages of the well known low-temperature organic binders and also the hightemperature inorganic binders, the l products maintaining continuous integration over wide ranges of temperature, from ordinary tem- 30 peratures up to that of'thermal disintegration of nuca.

A further object is to provide laminated mica products having new and useful properties .over increased temperature ranges, which new properties result from the employment of new types of mixed cooperating organic-inorganic substances a's'binders, as described herein. A further object is to provide laminated mica products, which when in the form of sheets, may originally possess flexibility at ordinary temperatures, thereby being adapted to be shaped as desired, and after heating retain to a large degree their bonded strength, even when heated to the decomposition temperature of mica, but which after having been heated to high temperatures lose their original flexibility upon cooling to ordinary temperatures, becoming rigid when cooled, in any desired formed shape.

55 strength sufficient for all commercial purposes A further object is to provide amica product,

and also retain its integration and good mechanical properties after cooling.

A further object is to provide a laminated mica product, for example a sheet, that maintains integration and high dielectric strength at all temperatures under all conditions of service up to the'point ofdecomposition of the mica.

A further object is to provide bonded products, for example products containing mica iiakes with or without other solids, in which a variety of adhesives consisting of mixed cooperating organic and inorganic substances are used, the substances separately and collectively constituting highly efcient bonding agents, for the purpose of extending the thermal usefulness of the product and its bonding adhesive several hundred degrees with retarding of the thermal decomposition of the organic constituent of saidadhesive.

Another object of the invention is to make available products, which at temperatures up to about 450 F. shall exhibit the advantages of well known organic bonded products, and at higher temperatures shall possess the advantages of the known inorganic bonded products; the new products thereby possessing the combined advantages of both the known organic and inorganic bonded products.

Other objects of the invention will be apparent to those skilled in the art upon reading the specifloation.y

As heretofore disclosed in the following: Boughton Patent 1,975,078, Oct. 2, 1934; Boughton Patent 1,975,079, Oct. 2, 1934; Boughton and Mansfield Patent 1,975,080, Oct. 2, 1934; and Boughton Patent, No. 2,004,030, June 4, 1935, compoundsof certain phosphoric acids, such as sodium metaphosphate; and also of the monoborates, such as sodium monoborate, are of great value in the compounding of inorganic adhesives, particularly in the manufacture of laminated mica products, because of the colloidal viscous nature of their aqueous solutions, and the glasslike condition of their fused forms.

In a search for new and advantageous binders for mica pieces or scales in the manufacture vof laminated products, it has been discovered that adhesives of the above noted inorganic type mayv be mixed with certain cooperating organic adhesives, with the result that bonded products may be produced possessing the combined advantages of both the well known organic bonded type, and the inorganic bonded type; the cooperating organic and inorganic adhesives both function as adhesives over their full temperature ranges, but the discovery has been made that the point of thermal decomposition of the organic adhesive has been advanced, so that before disintegration of the usual organic bonded product would take place, the inorganic adhesive has functioned with high efliciency, producing an eciently bonded product throughout the entire range of useful life.

The v organic bonding agents, which include shellac, copal, glyptal, and various other natural as well as synthetic resins, while exhibiting excellent bonding and other properties at the lower temperatures, fail at higher temperatures because of organic thermal decomposition, charring, etc. In some instances, the inorganic bonding materials when used alone, have been found not to have such high adhesion at lower temperatures as is occasionally desirable, but at higher ternperatures do, nevertheless, function as bonding media of unusual value, besides showing other useful properties.

We have discovered that by mixing binders of these two classes under certain conditions as described hereafter, a new and eminently useful group of bonding compositions can be made available in which in addition to possessing the advantages of each individual class of binders at its optimum working temperatures, the inorganic components inhibit the advance of thermal decomposition of the organic components, thereby extending their usefulness as binders; while the organic members at the lower and the inorganic members at higher. temperatures function with their usual eiliciency. Thus the new type of mixed binder functions to bond neutral materials and give optimum properties of the product over wider and more varied ranges of temperature than hitherto available.

As distinguished from the bonding materials of the mixed type just described, it is recognized that many general bonding and luting mixtures hitherto employed contain both organic and inorganic constituents, but in such cases the organic or the inorganic type of constituent alone is a true bonder for the particles and the other or others are present as llers or for some other mechanical or chemical purposes. Our new bonding materials differ from all such, however, in following the fundamental criterion that for any specific variety of discrete particle bonded, not only shall both the organic and the inorganic portions of the simple mixed composition be able to function separately as a bonding medium of recognized high efficiency, but between temperatures of about 617 F. and about 797 F. the advance of thermal decomposition of the organic component is inhibited and there is a reduction in charring. Thus in one typical instance the organic portion such as shellac is a mica binder of known value, as is also the inorganic part which is essentially an aqueous colloidal association of one or more inorganic colloids of the type described in the above noted Boughton Patent 2,004,030, for example, sodium metaphosphate, with or Without one or more other inorganic substances. Our new bonding mixtures invariably observe this criterion.

One of us has recently filed an application for patent on a new laminated mica plate bonded with a modern adhesive of the glyceryl borate type; (Boughton, Serial No. 661,864, filed March 20, 1933). This kind of bonding material cannot strictly be classified either as organic or inorganic, since it contains radicals of both kinds which are chemically combined. In this fact of chemical combination it is fundamentally different from mixtures involved in the present application. It does not follow the criterion stated above, because the organic radical (derived from glycerol, for example), is not in itself, a bonding material. Butthe chemical combination has been found to be a good binder for mica, and, therefore, can qualify in this invention as one of the constituents of a bonding mixture. Because of its amphoteric nature (containing as it does both organic and inorganic radicals in its molecule), it can be used as either the organic part or the inorganic part of a mixture of binders. 'I'his point will be further developed hereafter, where specific examples are considered. Some varieties of glyceryl phosphate also constitute an efficient binder for use in this invention.

Advantages of composite binders 'Ihe desirability of incorporating an inorganic constituent which is also an eliicientv binding agent into an organic adhesive is great with those bonded products that are required to withstand elevated temperatures, because of the superior action of the products at temperatures of organic destruction. By the dilution of the organic cornponent with an inorganic component, a smaller amount of charring and organic decomposition takes place when the product is heated above the normalv decomposition temperatures of the organic constituent. This is a novel and marked advantage. When the bond is organic alone, the bonded product is no more resistant to high temperatures than the bonding material itself. With such temperature resistant substances as mica, asbestos, and mineral wool, the bonding medium should be equally temperature resistant. This cannot happen when a purely organic binder is used.

By a suitable selection of cooperating organic and inorganic bonding components in the mixed binder, it is thus possible to extend the thermal usefulness of the bonded product as well as to maintain at higher temperatures its mechanical strength, dielectric strength, and electrical resistance, which otherwise would be lost through thermaldecomposition or volatilization of an organic bond. Thus the inorganic component not only functions as a bonding agent at lower temperatures, and retards the thermal decomposition of the organic component, but continues at higher the bonding functions of adhesion and integration, when the organic component would otherwise fail more quickly through thermal decomposition or loss, and so extends the usefulness of the bonded. product.

In the case of mica products, for example, laminated mica heater plate is used in flat irons and like appliances under compression. When the bond is organic alone, the binder is volatilized at the factory after the unit is assembled, leaving the mica pieces unbonded and held in position by compression only. Any disturbance of the pattern or assembly of mica pieces causes the burning out of the element. But when a cooperating inorganic bonding component is also present in the binder it maintains integration of the laminated sheets at temperatures up to thatat which the mica itself decomposes, and danger of burning out and destruction of the heating element is avoided.

Similarly in the case of commutator segments and other insulating parts, if through accident or some mechanical failure the motor should be vastly overheated, the presence of the inorganic constituent in the binder will preserve integration of the mica insulation long after the organic bonding constituent has completely broken. down.

It is thus seen that the present invention involves a marked improvement over prior art, and one not to be expected because all earlier experiments and all common practices in the general eld of bonding` had led to no such improvement in the arts of bonding as we have been able to effect by using as the cooperating inorganic constituents a member of the group of colloidal aqueous inorganic adhesives referred to in the above noted applications recently applied for by one or both of us.

In the accompanying drawing, which illustrate typical commercial products on an enlarged scale;-

Figure l illustrates in perspective a built-up mica plate or sheet, or other product, with a bonding agent comprising associated organic and inorganic adhesives;

Figure 2 illustrates in perspective an asbestos sheet or other asbestosproduct, containing` a bonding agent comprising associated organic and inorganic adhesives;

Figure 3 is a view partly in perspective and partly in section, of one type of laminated product consisting of built-up mica plates and asbestos sheet, all bonded together with associated organic and inorganic adhesives; and

Figures 4 and 5 are vertical sectional views of commercial laminated products consisting of layers of built-up mica plates and asbestos, all bonded together with associated organic and inorganic adhesives.

Examples Typical examples follow. It is to be emphasized that in no case need the formula nor the conditions of use be applicable to the entire field indicated. The exact proportions and conditions may be specific only to the example cited, but al1 are illustrative of the application of the general principles involved, which have been fully described above. The proportions or ingredients may be altered within these general principles to suit the requirements of particular products made. In

these examples Part A functions as the organic bonding constituent, and Part B as the inorganic bonding constituent of the mixture.

Example 1.-Lamlnated mica heater plate agent, continues to keep the plate integrated and functioning as a high temperature mica product,

up to temperatures at which mica itself decomposes (about 1200 F.).

Example 2.-Another formula for this product 'is as follows A. 1 part alcoholic shellac solution (0.5 lb. per. gallon). Less than 0.5% triethanolamine as mixing agent.

B. 1 part colloidal sodium metaphosphate binder as in Example 1, but with the quantities stated diluted with water to make about 14.8 uid ozs.

Example 3.-A third formula for this product is as follows A. Alcoholic shellac solution (0.5 lb. per gallon). B. An alcoholic solution of 3.5 lbs. per gallon of Example 4.-Laminatecl mica flexible (cold moldlng) plate A. 1 part of an alcoholic solution of about 34 B. of melted mixture consisting of about '74% of rosin, and about 26% of Red engine oil; (gravity of 24.6 to 26.1, a flash-point of 385 F. to 395 F., and a viscosity at 100 F. of 223 to 230.) Less than 0.5% triethanolamine as mixing agent.

part of an alcoholic solution of glyceryl borate as in Example 3, with 1.8% of added glycerol.

The product was of high quality in the lower temperatures, and non-flexible integration was maintained at higher temperatures up to 1200 F. This product is used in making armature slots, transformers and certain kinds of electrical heating appliances.

Example 5.-Laminated mica plate for commutator segments A. 1 part shellac water varnish (as in Example l) B. 2 parts colloidal sodium metaphosphate binder (as in Example 2).

Example 6,-A formula for use in making al molcling, thermoplastic plate is as follows A. 2 parts of an alcoholic solution of shellac containing 2.25 lbs. shellac per gallon of alcohol.

B. 1 part alcoholic solution of glyceryl borate as in Example 3, with 6% by volume of added glycerol.

Such a product is used for commutator V-rings, spools, troughs, and other cold molded forms.

Example 7.-Laminated mica flexible plate A. 1 part alcoholic santolite solution (2.251bs.

per gallon). A

B. 1 part alcoholic solution of glyceryl borate v with added glycerol asin Example 4.

Santolite is a commercial formaldehyde-toluene sulfonamide resin. y

The product was excellent and its properties duplicated those of Example 4.

Example 8.-,Another formula for segment plates is as follows A. 4 oz. Button shellac, dry. B. 0.56 oz. sodiummonoborate, dry.

The dry mixture is boiled with about 28.2 uid ozs. of water until solution is complete. An excellent plate is produced yielding rm and clearly punched segments. Integration is maintained up to about 1200 F.

Example 9.-Asbestos sheeting A. 1 part shellac solution (2.25 lbs. per-gallon of alcohol).

vB. 1 part glyceryl-monoboric a'cid solution. (4.5 oz. boric acid and 3.0 oz. glycerol heated to 356 F. and the reaction product then dissolved in anhydrous alcohol to make about 14.1 uid ozs.

Example 10.-Lamnated asbestos and mica A. 1 part of Bakelite )iK-4043. Less than 0.5%

of triethanolamine as mixing agent.

B. 1 part of colloidal sodium metaphosphate inorganic binder as in Example 1.

The Bakelite XK4043 is a phenolformaldehyde resin solution supplied und-er this name by the manufacturers and is thinned with toluene to make a solution containing 2.25 lbs. of solid per gallon.

The mixture of the two components was used to impregnate two sheets of long ber asbestos separately. Two layers of mica lm were then built upon one sheet and the other sheet laid over the mica layer. The whole was then dried and heated under pressure to eilect integration. Or two layers of built-up mica plate and an inner layer of asbestos could be assembled into an integral product in the same manner.

Example 11.-Molded mica powder A. 2 parts of Mowilith N (2 ozs. Mowilith N, a

commercial polymerized vinyl ester, in alcohol to make about 9.5 uid ozs.) Less than 0.5% triethanolamine as mixing agent.

B. 1 part colloidal sodium metaphosphate binder Aas in Example 1.

The mica powder was treated with enough of lthis mixed binder to hold the particles together,

and the :resulting mass molded, dried, and heated to 'temperatures varying between about 300 F. and about 1250 F., depending on the natureof the product desired.

Example 12. Lam1zateol mica heater plate V bonding material and inorganic Example 13h-Laminated mica plate A. 2 parts of glyceryl borate solution (3l/ lbs.

to the gallon of alcohol), 1% triethanolamine as mixing agent.

B. 1 part o1 colloidal sodium metaphosphate binder as in Example 1.

Example 14.-Built-up mica plate, and otherv bonded products A. 1 part of an alcoholic solution of about 34 B. of a melted mixture consisting of about 74% of rosin, and about 26% of Red engine oil as in Example 4. Y 1% of triethanolamine as mixing agent.

lB. 1 part of sodium glyceryl metaphosphate solution (about 4.4 ozs. of sodium metaphosphate and about 6 ozs. of glycerol dissolved in water,

' heated to 365 F. and the reaction product dissolved in water to make about 17.6 iluid ozs.).

Example 15.-Laminated mica fleible (cold molding) plate 4 A. 1 part of a 21/2 pounds per gallon solution of Manila copal gum in alcohol, containing approximately 8% of castor oil by-volume.

B. 1 part of glyceryl borate solution as in Example 4.

The plate is made by the standard methods of manufacture, and is of high quality.

It will be understood from the descriptiomand from the foregoing examples, that the products are bonded by an adhesive readily formed from a mixture of (A. and B.) designated organic and inorganic bonding constituents, and that either the organic or the inorganic bonding constituent of the mixture may be amphoteric in nature, that is, a chemical reaction product of organic and inorganic materials. Accordingly the terms organic and inorganic, claims, should be accorded such meaning and scope within the above definition of the adhesive as the accompanying context `of the admit or require.

We claimr- 1. A molded product containing discrete particles, said particles bonded by an adhesive consisting of intimately mixed cooperating organic bonding material, and the assembly thereafter being suitably baked, said cooperating organic and inorganic bonding materials being collectively and individually capable of bonding, and actually bonding, said discrete particles, said product being maintainedy integrated over a Wide range of temperature, said inorganic bonding material inhibiting vcharring and thermal decomposition of said cooperating organic bonding material when heated to approximately normal decomposition temperatures, and said product remaining integrated by said cooperating inorganic component of said adhesive at temperatures above that at which said cooperating organic bonding material is destroyed.

2. A molded product, as in claim 1, in which said discrete particles consist of associated asbestos fibres and mica flakes.

Wherever found in the appendedvr claims may 3. An integrated mica product. consisting of laminated mica flakes cemented together by an .adhesive consisting of intimately mixed cooperating organic bonding material and inorganic bonding material', and the assembly thereafterbeing suitabIybaked, said mixed cooperating organic Iintegrated by said cooperating inorganic component of said adhesive at temperatures above that at which said organic bonding material is destroyed. i

4. An integrated micaproduct consisting of laminated mica akes cemented together by an adhesive consisting of the intimately mixed cooperating agents comprising shellac varnish as'an organic constituent, and as an inorganic constituent a bonding aqueous association containing colloidal alkali metal metaphosphate, colloidal alkali metal monoborate, and dipotassium orthophosphate, and the assembly thereafter being suitably baked, said mixed cooperating organic and inorganic bonding materials being collectively and individually capable of bonding, and actually bonding, said mica iiakes, said product being maintained integrated by said adhesive over a Awide range of temperature, said inorganic constituent inhibiting charring and thermal decom-A .position of said shellac when heated to approximately normal decomposition,temperatures, and said product remaining integrated by the cooperating inorganic components of said adhesive at temperatures above that` at which vsaid shellac varnish is destroyed.

5. An integrated mica product, as inclaim 4, ln which the inorganic bonding constituentcomprises an aqueous association of colloidal sodium metaphosphate, colloidal sodium monoborate, and dipotassium orthophosphate.

6. An integrated mica product, as in claim 4,

in which the organic bonding constituent comprises shellac-water-Varnish.

7. An integrated mica product, as in claim 4, in which the organic bonding constituent comprises shellac-Water-varnish, and the inorganic bonding constituent comprises an aqueous association of colloidal sodium metaphosphate, colloidal sodium monoborate, and dipbtassium orthophosphate.

8. An integrated mica product consisting of laminated mica flakes cemented together by an adhesive consisting of the intimately mixed cooperating agents comprising alcoholic shellac varnish as an organic constituent, and as an inorganic constituent a glyceryl borate, and the assembly thereafter being suitably baked, said mixed cooperating organic and inorganic constituents being collectivelyand individually capable of bonding, and actually bonding, said mica A iiakes, said product being maintained integrated by saiclv adhesive over a Wide range of temperatures, said borate inhibiting charring and thermal decomposition of said shellac when heated to approximately normal decompositionV temperatures, and said product' remaining integrated by ysaid cooperating borate component of said adhesive at temperatures above that at which said shellac would be destroyed, and its inorganic residue functioning as abond for said mica flakes at temperatures-above that at which all organic constituents have been destroyed.

9. An integrated flexible mica product consisting of laminated mica akes cemented together by an adhesive consisting of the intimately mixed cooperating agents comprising an alcoholic solution containing rosin and Red engine oil as an organic constituent, and as an inorganic constituent an alcoholic solution of a glyceryl borate, and the assembly thereafter being suitably baked, said mixed cooperating organic and inorganic constituents being collectively and individually capable of bonding, and actually bonding, said mica flakes, said product being maintained integrated by said adhesive over a Wide range of temperatures, said borate inhibiting charring and thermal decomposition of said rosin and Red engine oil when heated to approximately normal decomposition temperatures, and said product remaining integrated by said cooperating borate component of said adhesive at temperatures above that at which said rosin and Red engine oil are destroyed, and its inorganic residue functioning as a bond for said mica flakes at temperatures above that at which all organic constituents have been destroyed.

10. An integrated flexible mica product consisting of laminated mica flakes cemented together by van adhesive containing the mixed cooperating agents comprising .shellac as an organic constituent dissolved in an inorganic constituent consisting of an aqueous solution of col- Vloidal alkali metal monoborate, and the assemvclaim 10, in which the inorganic constituent consists of sodium monoborate. l

V12. An integrated iiexible mica product, as in claim 8, in which the organic constituent cmg;I prises an alcoholic solution of Santolite, and t inorganic constituent comprises an alcoholic soluti`n of a glyceryl borate and an excess of glycerol.

13. An integrated flexible fcold molding mica product, as in claim 8, in lwhich the organic constituent comprises an .alcoholic solution of manila copal gum and castorI oil, and the inorganic constituent an alcoholic solution of a glyceryl borate and an excess of glycerol.

14. Asbestos Vsheeting consisting of asbestos bres saturated with an adhesive containing the mixed cooperating agents comprising an alcoholic solution of shellac as an organic constituent, and asan inorganic constituent glyceryl monoboric acid, and the assembly thereafter being suitably and thermal decomposition of said sheilac when inorganic residue functioning as a bond for said heated to approximately normal decomposition asbesto.: fibres at temperatures above that at temperatures, and said sheeting remaining inte-t which al1 organic constituents have been degrated by the cooperating monoboric acid constroyed.

stit-uent of said adhesive at temperatures above WILLIS A. BOUGHTON. that at which said shellac is destroyed, and its WILLIAM R. MANSFIELD. 

